Tuning device for broadcast receivers



Se t. 14, 1937. A. SPGTTEL I 2,092,991

TUNING DEVICE FOR BROADCAST RECEIVERS Filed Dec. 21, 1934 INVENTOR 4001f JPW' 71-2 ATTORN EY Patented Sept. 14, 1937 Q'rpiNING FDR saosnonsrf i ."nsoslvcns 1 Adolf Spiitte'LBerlin, Germany, assign'orto' Telefunken .Gesellschaft fiir Drahtlose Telegraphic m. b. H., ,-Berlin',-Germany, a corporation of Germany Application December 21, 1934, Serial No. 758,587 In Germany December 28, 1933 3 Claims.

In broadcast receiving sets and similar apparatus in which tuning means must be set, a knob or the like is invariably provided by the agency of which adjustment isfeasible from the outside. Because of the great number of stations which may mostly be received by means of a modern receiver apparatus, it is desirableto be enabled to effect fine adjustment. In such cases, according to the prior art, a vernier knob has mostly been provided adjacent to the knob ingear ratio, and in the other direction, inside a certain range, being transferred with a reduced gear ratio to the same tuning means.

The basic idea of the invention will be explained in more detail by reference to the drawing wherein Fig. 1 is an exemplified embodiment thereof, and Figs. 2 and 3 are sectional views respectively on lines 2- -2 and 33 of Fig. 1. Reference character I denotes the tuning knob which is secured upon a spindle 2 by suitable means such as the screw i. The spindle is suitably supported in end brackets l5 and I5 which are provided with bearing members l6 and [6' respectively, said bearing members serving to permit rotary motion only of the spindle 2 and its associated tuning knob I. Fixedly connected with this spindle for rotation therewith are a disk 3 and a drive lever 4, thedisk 3 being mounted to have in addition slight longitudinal movement on the spindle. Another disk fi'which at one place carries a pin 8, is rotatably disposed upon the spindle 2. Cooperating with the said disk 5 is a disk 8 seated on another spindle 1, said disk 8 being rigidly connected through a cylindrical piece 9 with a disk Ill. The assembly 8, 9, I8 is journalled, i. e., in the present case, it

, is rotatably seated upon the spindle l. The disk I co-operates with the disk 3. The spindle H, which is to be driven and on which the tuning means, say, the rotary condenser or condensers are seated, is in coupling relation with the disk 8 through disk l2. Disposed upon the spindle 2 between stop I3 and disk 3 and between stop l4 and disk 5 are expansion springs 13,14, respectively which press the disks 3 and 5 against the respective disks Ill and 8. The tension of these springs is so chosen that between disks 8' and 5 there prevails more friction than between the disks 3 and I0.

Fig. 3 discloses a suitable form of mounting for the disk 3 on the shaft 2 to provide slight.

longitudinalmovement due to the keyway 2 and r at the same time rotary movement with the spindle or shaft 2. Fig. 2 shows the manner. of

loosely mounting the disk 5 on the shaft 2, without a keyway, whereby the disk 5 may rotate independently of the shaft]. The washer 5' prevents lateral movement of the disk 5 in a direction to the right.

The operation of the arrangement is as folmitted to the spindle I l by way of the arm 4, pin

6, and disks 5, 8 and I2. Incidentally, the disks 3 and I 0 are in frictional engagement upon each other. When knob I is turned in the opposite sense, the lever 4 will recede from the pin 6 so that now rotation or torque is transmitted by way of the disks 3, I8, 8 and I2, to the spindle II. The pin 6 in the presence of rotation in this sense is also turned slightly, so that this motion will thus not be impeded. It is only when the tuning knob is again turned back as far as the stop 8 that there is a direct drive (through idler 8) from shaft 2 to shaft H. In other words, manipulation is so that first the desired station is roughly tuned in, whereupon, by backward motion, fine setting is secured by a drive through a step down gear ratio.

What is essential in the building and disposition of the bodies 8, 9, I0, is that the two disks 8 and It] must be fixedly intercoupled in both directions. Their mutual distance on spindle 1 need not be fixed. To compensate friction it may even be desirable to make the intervening distance regulable or variable.

I claim: 7

1. Tuning apparatus for radio receivers com prising a tuning knob aflixed to an operating shaft, both ofwhich are capable of rotary motion only, a tuning shaft, mechanism for transmitting motion from said operating shaft to said tuning shaft when the tuning'knob is operated in one direction, said mechanism including a friction drive, a second mechanism operative when the tuning knob is operated in the opposite direction, for transmitting motion from said operating shaft to said tuning shaft at a different rate from the motion transmitted through the first menmitting motion directly from said operating] shaft to said tuning shaft and constituting a rough adjustment of the tuning shaft, a second drive mechanism between said operating shaft and said tuning shaft for transferring motion from said operating shaft to said tuning shaft and constituting a fine adjustment of the tuning shaft, said second drive mechanism including a friction drive, said friction drive being adjusted to slip during the interval that the first mentioned drive mechanism is transmitting motion.

3. Mechanism of the class described comprising a driving shaft, a driven shaft, a disk mounted on said driving shaft for rotation therewith, a, disk adapted to be driven from the first mentioned disk, means for frictionally engaging said disks, means for transferring motion from said second disk to the driven shaft, a disk freely mounted on said driving shaft, means for transferring motion from said freely mounted disk to said driven shaft, and means for transferring motion from said driving shaft to said freely mounted disk. 

